In todays' industry, there is a large demand for devices that sense the position of a remotedly located target and displays the information or feeds the information to industrial control systems. It requires quite a simple technology and an inexpensive product package to provide such a position-sensing and the indicating device when the error allowable in the automatic position sensing technology is comparable to one quarter or to one eighth of an inch while it requires a challenging and expensive technology to provide a position sensing device with a high accuracy tolerating an error of a few thousandth of an inch. The former type devices may be applied to the level sensors used for automatically detecting the fluid level in reservoirs and tanks and to the various control devices used in material handling devices, while the latter types are used in automated machine and forming tools. Most of the present day level sensors providing a continuous reading on the fluid level in the reservoirs and tanks are either expensive or lack simplicity and reliability.
The primary object of the present invention is to provide a position-sensing device that utilizes the principle of variable resistance against electric current.
Another object of the present invention is to provide a position-sensing device that utilizes two counter-balancing variable resistance circuits wherein the output is independent of the contact resistance between the circuit wires and the sliding contact conductor.
A further object of the present invention is to provide a totally enclosed position-sensing device wherein the functional components are totally isolated from the surrounding fluids.
Yet another object of the present invention is to provide a position-sensing device of explosion-proof grade.
Yet a further object of the present invention is to provide a position-sensing device that is highly reliable and inexpensive.
These and other objects of the present invention will become clear as the description thereof proceeds.